Telephone system



June 10, 1941. Pos1- 2,244,920

` TELEPHONE SYSTEM Filed July 31, 19:59 2 sheetsheet 1 HELMUT P05 7'June 10, 1941. H pgs-- TELEPHONE SYSTEM Filed .my 51, 1959 2Sheets-Sheei'. 2

f [Nif/WOR.- HEL/W07F POST 1347414.

A TTORNEV.

Patented June 10, 1941 TELEPHONE SYSTEM Helmut Post,Berlin-Charlottenburg, Germany,

assignor to Fides Gesellschaft fr die Verwaltung und Verwertung vongewerblichen Schutzrechten mit beschrnkter Haftung, Berlin, Germany, acorporation of Germany Application July 31, 1939, Serial No. 287,517 InGermany August 8, 1938 7 Claims.

The present invention relates to telephone systems with main andsub-exchanges in which the sub-exchanges not provided with batteryfeeding arrangements are connected with the main exchange over a numberof junctions. More particularly it relates to arrangements for providingbusy indication of subscribers lines at such a sub-exchange.

In known arrangements with a number of junctions Ibetwen main andsub-exchange indication that -a subscribers line is engaged is easilygiven since the sub-exchanges are provided with local battery feed sothat the engaged subscribers line can be guarded, in the manner usual inselector systems, over a special auxiliary conductor in a local circuitofthe sub-exchange. Difficulties occur when the sub-exchange has nobattery.

The present invention relates to a method of solving the problem ofconnecting sub-exchanges not provided with battery feed with the mainexchange lover a number of two-conductor junctions and of connecting acalling sub-exchange subscriber to a free junction line. This result isobtained in that, in the sub-exchange, switching arrangements areassociated with each subscriber which, on a call from a subscriber, areso controlled from the main exchange over one of the junction linescorresponding to the junction to be used for setting up the connection,that the calling subscriber has access only to the main ex change overthis junction.

The invention is illustrated with respect to an embodiment shown inFigs. 1 and 2, Fig. 2 being a continuation of the system tothe `right ofFig. 1, in which a telephone installation including a subexchange UAwithout local battery feed is connected to a main exchange I-IA over twolines (VLI, VLII).

For connecting a sub-exchange subscriber to the junction extending tothe main exchange a selector is provided at each junction in thesubexchange which selector is set by impulses transmitted from the mainexchange and each subscriber is alsoI associated with a relay for eachjunction. For outgoing calls one junction (VLI) has prior facilities`and for incoming calls the other junction line (VLII) has priorfacilities.

In the main exchange, a switch mechanism (wiper mw) is provided for eachjunction which switch means are positioned synchronously with thesub-exchange selector when impulses are transmitted for setting thesub-exchange selector. For outgoing and incoming connections it servesto indicate that the calling sub-exchange subscribers line is engagedand, moreover, for outgoing connections it switches in the callingsubscribe-rs meter at the main exchange.

For testing the condition of the subscribers line at the main exchange,testing arrangements are associated with each junction and are connectedto the Wipers of the previously mentioned' switch in which both contactscorresponding to the individual subi-exchange subscribers in the contactbanks of the switches for both lines are connected together. Whenindication is given that a subscribers line is engaged at the switch ofone junction line the testing apparatus at the switch of the otherjunction line is seized when the same subscriber has been selected.

In the embodiment the setting up of the connections of the telephonesystem takes place in the following manner:

In the normal condition of the system a permanent current circuit iscompleted over each junction and prepares call circuits over eachjunction for all the subscribers of the sub-exchange UA. The permanentcurrent circuit over the junction line VLI extends over: earth,battery,A winding I of relay XI, contacts43I,42y,4Ia34lc,wipermwl inzero position, zit-conductor of the junction line VLI, contact ISdwI orcontact IIIuI and wiper wII in zero position, wiper wI2 in zeroposition, contact II mI2, relays MI I, MIZ, earth. In this circuitrelays MI-I and MI2 are energised so that their contacts are in theposition shown. Therefore a multipled call circuit for all subscribersof the sub-exchange UA is prepared over the junction VLI to the mainexchange HA.

The permanent current circuit over the junction line VLII extends in acorresponding manner over the a-conductor of this junction so that, inthe sub-exchange, the relays M2I and M22 of the junction line VLH areenergised. These relays have their contacts in the positions shown sothat over the junction VLII a multiply-connected call circuit isprepared for all subscribers of the sub-exchange UA. By means ofthe'relays (e. g. A2, B2) associated with subscribers of each junctionthe two multiply-connected call circuits corresponding to the twojunctions are made accessible to all subscribers of the sub-exchange UA.In the embodiment the arrangement is such that on a call from asubscriber when both junction lines are free, a call circuit is iirstcompleted over the junction line VLI in that the relay X2 of thejunction line VLII for receiving the call impulse is shortecircuitedover contact mdb oi the relay B of the junction line VLI so that itcannot be operated by the call and only the relay XI can be energised.This circuit, whenV yand 89122, earth. 'Ihe relay XI by closing contact59ml locks its winding II over the resistance Wil 3 in a circuit whichafter the switch is stepped on extends over wiper mw2, contacts 5Ixl',Elpl, (or, later, 52o) and the resistanceWi I-2. Contact llilzrl`operates when relay XIV is energised and breaks the permanentcurrent-.circuit extending over the a-conductor of the junction' lineVLIso that, in the sub-exchange UA, the relayslVIll and MIZ aredisconnected. These two relays al' low their operated contacts 'Iml2,Bmll and-- IImIZ to open interrupting the multiply-connectedcallcircuitin the sub-exchange and the permanent current circuit while the rotarymagnet Dwl ofi the selector in the subi-exchange UA is-connectedtol theb-c'onductor of the junction VLI` by the closing of contact I'ImII andthus the followingcircuit is' completed: earth; battery; winding I of.relay'K, contacts Elly, wiper mw .ln zero position, contact 55g,beconductor of the junction line VLI, contacts lul, IIm'I-I, rotarymagnet Dwl, earth. In this circuit'relay K and rotary magnet Dwl areenergised. Winding I of relay A1. isv connected to the a-conductor ofthe jun'ctionline VLIby the closingof contact 35k so that, after theselector in the sub-exchange is stepped-on bythe rotarymagnet Dwlenergising over'the Contact IZdwIa which is operated by the rotarymagnet Dwl, the following. circuit is completed: earth, battery,"windingI of relay A, contactsll'ila, 33a., 3811, 33ml, 35k, wiper mw! in zeroposition, aeconduct'or oflthe junction line VLI, contact I2`dw'l, wiperwl3 on the se'gment I-I, resistance Wz', earth. In this circuit relay Ais energised' so that cont'actlla' closes and causes theirotarymagnetDmw of the switch in the main exchange to energise over: earth,battery, rotary magnetl Dmw, contactsA'Iq, 48a, 5b, 49pl, earth. Theswitch mechanism in the main exchange is advanced by. one step. Relay Yis energised'over itsfwindingIv bythe closing of contact Bldmw so that.as contact Gil'y is'opened the winding I of relay K is disconnected; Thecircuit extending over the b-conductor of-the junction VLI for therotary magnet :Dwl is interrupted after thestepping-onor" the Vswitcha-t the main exchangeat AWiper mw3,'.so that the circuit completed' forthe Winding I of relay A over the a-conductor of the junction VLIisdisconnected by the opening of cont'actIZdwl. Relay A is thusdisconnected and breaks the'circuit of the rotary magnet' Dmw at contactso sin'cercontact 3 Idmw is opened the relay'Y. restores.

During the period during which relay Y is energised'` relay K'is notenergised, the test circuit f'or. determining the calling subscriber isApreparedY inv that battery potential is connected to thea-conductorover the resistance Will and contactyS-Iy Vand earth potential isconnected to the'b-conductor'over the contact Elk and the test relayBiByl means of thebatter'ypotential on the a-conductor inthe subexchangerelay AI, conn'ectedoverwiper wII of the subscriber Tnl (notL shown),isenergised in order to determine whether this subscriber is thecalling' subscriber. Ifthe subscriber (not shown), isfalready connectedtothe junction line VLII then,` since his relay Bl is energised, anenergisation of relay AI is prevented so that the subscribersconversation over the other junction line is not disturbed.

Since, in the present case, the subscriber T712 makes a call, after theswitch is iirst stepped-on there is still no test circuit completed andafter the energisation of relay Y, and the closing of contact liy, thewinding I of relay K, is energised again over: earth, battery, winding Iof relay K, contact Elly, resistance W112i), contacts lb, 53D. wiper`mm2 on segment l5, earth. The relay K over its contactv 25k connectsbattery to the bconductor. The interaction described above is repeatedso that in the sub-exchange the selector g is advanced by. a furtherstep and by sending back an impulse over the a-conductor of the junctionVLI theY relay A in the main exchange HA is energised and thus theswitch in the main exchange is also advanced by a further step. Afterthe second step relay A2 is energised as long as relay Y is energisedover:'earth, battery, resistancev Will, contacts 3131, 33ml, wiper mwlon segment I-6,' a-conductor of the junction line VLI, contact Iul,wiper wII on contact 2, winding I of relay A2, contact IbZ, earth. Therelay A2Y disconnects the calling subscriber T112 from the junctionVLII. Moreover, the calling subscriber is connected over contact 3&2with a branch, used for all subscribers, multipledto the a-conductor atwhich branch a-condenser-is cone nected for bridging overthe A-relay,while at contact a2 a corresponding connection is eiective for bridgingover the relay UI at their-com ductor. In this speciali arrangement twocondensers only are used' for.` bridging over the. re' lays at eachconductor for all the subscribers.- s After these operations,l takingplace over` the subscribers loop the followingcircuit is completed:earth, battery,'resistance Will l, contacts Bly, 33ml, wiper mwl onAsegment l-B, a-conductor of the junction line VLI, contact IBdwI, wiperwl2, on the contact 2, windingII- of relay A2; contact l'b2, subscriberT'rL'Z, contactsqSAbZ, 5a'2, relay UI, contact l9ul, earth. In thiscircuit relay A2 remains energised while relay Ul is energised so that,with disconnection of earth at contact ISuI and of the rotary magnetDwlIat contact I Sul, the b-conductor of the junction line VLI between thecalling subscriber 'In2 and the main exchange HA is switched throughvover the contact 2Ilul. @very the calling subscribers loop the relay B,connected' to the b-conductor of the junction line VLI, is now energisedin series with relays UI and A2 since contact 6 Ik is closed'. By'theopening of contact 50h a furthere'ner.- gisation of the rotary magnetDmwis prevented. Relay'Y now restores and in` place'of the resistanceWill connects the relay A to thea-"conductor so that now this relay isenergised in series with the relays A2, Ul and'B.

Meanwhile, by the closing of contact 59o, 'the relay RI is energisedover the choke DrI for the purpose of starting-up the pre-selector VWI.Further, contact 63h closes connecting the winding I of relay V so that,contact I 'I lv closing, the following circuit is completed (l): earth,battery, windings I and II of relay PI, contacts I Illy; IIIU, wiper'mw'vV on contact 2, resistance WZIS, earth. At contact I09pl' the highresistance winding II of relay Pl is short-circuited so that at the mainexchange the calling subscribers line vis indicated as being busy.Should 'the subscriber T122 now be called over the junction line VLIIaccording to the positioning of the wiper mwl (IDI, in the mannerexplained later, the relay P2 is not energised. As a result earthpotential (compare VLIz'earth, Wz'l5,l Blpl) is not corinected over ao2-contact to the b-conductor of the junction line VLII to the seriesfinal selector, as can be seen in the case of the junction VLI, wherebya relay operated up till the reply of the required subscriber of theb-conductor of the final selector is restored and on transmission of anengaged signal from the final selector the test conductor c of thejunction line of the sub-exchange is disconnected so that this junctionline is released. A further connection tothe subscriber already engagedis thus prevented. It can be seen that in the main exchange HA the lineofthe calling sub-exchange subscriber 'I'n2 is marked asv being engagedby means of the relay PI so that connections over the otherline cannotbe put through to him. v,

If, in the meanwhile, the'pre-selector VWI started up by the callimpulse, has-found a free selector, then, in known manner, thev relay TIis energised whereby the calling subscriber is switched through over thewipers of the preselector VWI to the numerical impulse receiver.

When the subscriber T112 operates his dial switch the relays A and B arerestored intermittently by interruption of the subscribers loop so thatby the corresponding interruption of the contact 69h a transfer ofimpulses for setting the subsequent numerical impulse receiver occurs.When the required subscriber has been reached after transmission of thenecessary impulse trains, there follows transmission of ringing current.When he replies, the ringing current is disconnected in the known mannerand a metering impulse is transmitted over the test conductor by whichthe winding I of relay Z is operated. By the closing of contact H52 themeter Z2 corresponding to the calling subscriber T1712 and connected tocontact 2 over the wiper mw of the switch in the main exchange, isoperated.

When the calling subscriber hangs up at the end of a conversation therelays A and B and, a short While later, relays A2 and UI are restoredby the interruption of the subscribers loop. By the opening of contact69h the numerical impulse receiver is released as well as thepreselector VWI which, over its wiper c, after it has restored tonormal, short-circuits the winding II of relay V which after thedisconnection of winding I has hitherto remained energised over contact16o. The holding circuit of winding II of relay XI is interrupted by theopening of contact 52o so that, during the following return movement ofthe selector in the sub-exchange, a testing by a calling subscriber isprevented by means of the relay B (contact 62M open). After the releaseof relay V and on the opening of contact I I lo relay PI is alsodisconnected. By the closing of contact 53o winding I of relay K isfurther venergised so that now the stepping-on of the subexchangeselector which is of not further interest, and of the switch in the mainexchange to their normal positions, takes place. When the subexchangeselector has taken its nal step, as long as the rotary magnet Dwl isstill energised, relays MII and MIZ are energised over contact Iwl overthe a-conductor of the junction line VLI and resistance Will) and overthe Winding I of relay XI so that when contact IImI2 closes after thedisconnection of rotary magnet Dwl the permanent current circuit(already indicated) for the multiple connection of the call circuits isclosed.

As described above the relay B in the main eX- change is energisedduring the existence of a con.. nection over the junctionline VLI sothat at the junction line by the opening of contact' |0417 the shortAcircuit for winding I or relay X2 is removed. As a result a furthercall for setting up an outgoing connection from the junction line VLII.can be undertaken inone of` the ways described vabove in connectionvwith the junction line'VLI. TheA switching arrangements of the junctionline VLII, 'not shown in the drawings, operate in the same manner asthoseexplained for the junction line VLI. 'The connected subscribersline is locked by means of the relay P2 over the wiper mw5 (II).

If instead of' an outgoing connection an incoming connection is set upthen the final selector LW is first set by means of the characteristicdigit of the sub-exchange UA. The i'irial selector LW then tests whichline is free in known manner, it then tests, therefore, the nextjunctio-n line VLII since this'l is the first line conected in itscontact bank. If this line isengaged it steps on to the junction lineVLI. When this is free the relays Z, Y and TI are energised over thec-wiper `of the final selector LW. Over the blconductor the relay K(winding II) is energised, from the series final selector LW. The otherswitching operations (energising of relays Q, V, XI) are performed afterthe rotary magnet DwI has been connected to the b-conductor by theinterruption of the permanent current circuit over the a-conductor (42g)by the relay K operated by the impulses transmitted over theb-conductor; this switch (44k) in the main exchange and the selector(21k) in the hub-exchange are stepped on in synchronism. In the mainexchange when these have been set, the relay PI tests to determine ifvthe required subscriber marked by the positioning of the wiper mw5 inthe main exchange is free. Should this be the case, relay PI operatesand after disconnecting the Winding II of relay K (Y restores after theimpulse transmission) over the contact 8IpI, earth is connected to thebconductor of the final selector so that a call is initiated. Therequired subscriber is connected by the operation of the correspondingA-relay over the wiper wII after the selector in the subexchange hasbeen set in position. At contact EEpI relay Bis connected to theb-conductor.

When the required subscriber replies the relays A, UI, B operate overthe subscribers loop in series with the already energised A-relay of therequired subscriber. ringing current in the final selector is broughtabout by the opening of contact o. Further operations are not ofinterest.

It should be noted that all switching operations described for thejunction VLI in the setting-up of outgoing or incoming connections areperformed in the manner when using the junction VLII.

I claim:

l. In a telephone system having main and subexchanges and two conductortrunk lines connecting said exchanges, means in the main exchange forsupplying all battery feed to the subexchanges, subscribers lines in thesub-exchange normally common to a plurality of said trunk lines, step bystep switching devices on each trunk line, means operated b-y theinitiation of a call on a subscribers line for operating the switchingdevices of one trunk line to complete a connection from the subscribersline over the trunk line to the main exchange, one of the switchingdevices on each trunk line located in the main The disconnection ofvexchange and operating to preventl a connection being set-,up tothecalling subscribers over other trunk lines. 2. A telephone systemv asYclaimed in claim `1 wherein the switching ydevice of a trunk line vinthey main exchange is operated in a manner distinctive of the callingline.v Y

3. In a telephone system having a plurality of trunk lines connecting asub-exchange to a main exchange, subscribers lines in the sub-exchangenormallyiconnected to a plurality of said trunk lines, a switchingarrangement in the main exchange for each trunk linev operated 4when acall is extended either to or` from a line in the subexchange; saidarrangement always operated in a manner distinctively associated Ywiththe line in the'sub-exchange to or from which the call istextended. y

- 4;V In a telephone system having main and subexchanges-'with trunklines interconnecting them, means for supplying al1 batteryy feed tothesubexchange over said trunk lines, subscribers lines in thesub-exchange,a common circuit including all of said lines and said trunk lines, saidcircuit controlled from any line to extend a connection over one of-saidtrunk lines, switching devices infthe main exchange for each trunk lineand operated thereover under control of said common circuit to mark theline calling as busy.

5. A telephone system as claimed in claim 4 wherein there is also meansfor operating said switching devices whenever a call is extended fromthe main exchange to a subscribers line in the sub-exchange. y Y

6. A telephone system as claimed in claim 4 wherein there are alsoswitching devices for each trunk line in the sub-exchange and meanswhereby the switching devicesY of each trunk are operated insynchronism. g

7. In a telephone system, a main and a subexchange, two conductor trunklines connecting said exchanges, a step by step switch for each trunkline located inv the main exchange, means for operating one of saidswitches either on calls to or from the main exchange when theassociated trunk line is used, said switch always operated in adistinctive mannerfdependent on the line inthe sub-exchange included inthecall, means con.- trolled by each switch for marking the associatedline in the sub-exchange busy and testing means tion of lines in thesub-exchange.

HELMUT POST.

